1. Field of the Invention
This invention relates to a novel and improved magnetic disk information storage apparatus.
2. Description of the Prior Art
Magnetic disk files have been used for many years as bulk memories in data processing equipment. These magnetic disk files consist of a housing in which one or more flat disks are rotated at high speed. Magnetic recording material is deposited on one or both faces of each disk. Recording heads are arranged adjacent each recording face of the disks to read and write data upon the recording material.
Recording heads have been developed which float upon a thin film of air generated by a rapidly rotating disk. These recording heads have become known as flying heads. Flying heads are known which are always out of contact with an adjacent disk surface. However, in low cost magnetic disk files it is desirable that when the disks are not rotating each flying head should rest upon a portion of its adjacent disk surface which is not used for data recording.
With this type of flying head operation, the flying head is touching the disk surface below predetermined disk rotation speed, and each time the flying head takes off from or lands upon the disk surface particulate matter might be generated. As the flying heads float 50 micor-centimeters or less, above the disk surface, this particulate matter could interfere with floating head and thus must be removed from the disk file housing.
When the magnetic disks are rotated by a shaft which passes through the housing via a bearing, this bearing is a potential source of particulate matter and contamination which could interfere with flying head operation unless entry of this particulate matter and contamination is prevented.
In U.S. Pat. No. 3,710,357 (Ser. No. 51,867) to W. S. Buslik, there is described a magnetic disk storage file within a sealed enclosure. A rotatable hub is mounted on a drive spindle and supports an annular magnetic disk, an annular filter upstanding from the hub and a fin structure supported by the filter. Rotation of the spindle and hub also rotates the filter and fin structure and causes circulation of air for cooling and cleaning purposes around the disk annulus and through the filter by way of apertures in the hub. In such apparatus, a negative pressure region is created in the vicinity of the hub which could operate to draw contaminants through the spindle bearing. U.S. Pat. No. 3,489,800 (Ser. No. 231,320) to Cuzner also describes a magnetic disk apparatus having a sealed disk module and a filtering arrangement therefor. Rotation of a disk mounted on a hub and spindle assembly causes motion of air towards the disk periphery as in the Buslik U.S. Pat. No. 3,710,357 referred to above. The module is formed with a lower chamber, communication with which is by way of a main filter located beyond the disk periphery and a return port through which circulated air may return to the hub region. As with the Buslik arrangement, a negative pressure region is created in the vicinity of the hub but this is relieved by an externally mounted breather filter also located near the hub. The breather filter ensures that the pressure in the hub region is maintained at or near external atmospheric pressure. The possibility of contaminants entering the module via the spindle bearing is thus reduced, but not prevented.